What are the steps to decrease one hour from date and time using SQL?

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Assuming you want to decrease one hour from the current date and time, here are the steps:

1. Use the GETDATE() function to retrieve the current date and time.
2. Use the DATEADD function to subtract one hour from the current datetime value. The DATEADD function takes three parameters: the interval (in this case, 'hour'), the number to subtract (in this case, '1'), and the datetime value to subtract from (in this case, getdate()).
3. Format the resulting datetime value in the desired format using the CONVERT function.

Here's an example SQL query that demonstrates these steps:

SELECT CONVERT(varchar, DATEADD(hour, -1, GETDATE()), 120) as decreased_datetime;

This will return a single column with the datetime value decreased by one hour, formatted as 'YYYY-MM-DD HH:MI:SS'.